1. Technical Field
The embodiments described herein are related to automated environment control system operation and more particularly, to systems and methods for controlling the temperature of the room based on occupancy.
2. Related Art
Heating, ventilating, and air conditioning (HVAC) systems provide control over the indoor environment of buildings through heating, cooling, and air circulation. Rising energy costs have driven manufacturers to make an effort to make these systems more energy efficient; however, even the most energy efficient HVAC systems can still waste energy by heating or cooling unoccupied spaces within a building. For example, hotels can have numerous unoccupied guest rooms. Heating and cooling these unoccupied rooms is not only a waste of energy, but also of money. Heating and cooling unoccupied areas of hotel can significantly increase the hotel's utility bills. Heating and cooling of unoccupied areas of residential properties can also have a significant impact on utility bills. For example, in a multi-story home, occupants may be downstairs during the day and move upstairs at night. Accordingly, it can be inefficient and costly to heat or cool the upstairs during the day and the downstairs at night.
Office buildings provide another example of a type of building that can have widely variable occupancy rates where the HVAC system can waste significant amounts of energy heating and cooling unoccupied portions of the building. During the day, many offices are likely to be occupied, while on weekends or during evenings, much of the building is likely to be vacant. Often building owners or managers will simply turn off the HVAC services to the building during low occupancy periods; however, this leaves anyone occupying the building during these periods without HVAC services, which can result in a stuffy and/or uncomfortably hot or cold working environment. Furthermore, this all or nothing approach does not take into account portions of the building that can remain unoccupied even during the peak occupancy hours (e.g., vacant offices). Conventional HVAC systems do not provide the ability to limit HVAC services to occupied portions of the building.
Some manufactures have attempted to balance the needs of energy efficiency with comfort of occupants of a building by providing systems that can cycle HVAC systems on and off in order to maintain temperatures of unoccupied portions of the building within a certain predefined range. However, these conventional approaches must sacrifice either energy efficiency or occupant comfort. For example, some conventional HVAC systems, particularly in hotels and resorts, sacrifice energy efficiency in order to maintain the temperatures of unoccupied rooms within a very narrow temperature range in order to ensure that if an occupant enters a previously unoccupied portion of the building, the temperatures are still within a comfortable range. Such a system is often used in hotel rooms to attempt to conserve energy by limiting the heating or cooling of the room while the room is unoccupied. But the HVAC system is configured to maintain the temperatures within a narrow range so that should a hotel guest return to his or her room, the room will still be at a relatively comfortable temperature. To maintain the temperatures within this narrow temperature range requires that the HVAC system still run relatively frequently, sacrificing energy savings.
Other conventional HVAC systems sacrifice occupant comfort in exchange for increased energy savings. For example, the HVAC system can be configured to shut off entirely when the room is unoccupied. While this approach can result in significant energy savings by limiting or stopping HVAC services to unoccupied rooms, the temperatures of the room can become extremely uncomfortable for occupants entering the previously unoccupied room. Furthermore, occupants returning to a room that is too hot may adjust the HVAC system to a much lower setpoint in order to more quickly bring the temperature of the room down to a comfortable range, which can sacrifice much of the energy savings provided by shutting down the HVAC system while the room was unoccupied.
Another problem with conventional techniques for reducing the energy consumption of a HVAC system is the inability of such systems to accurately determine whether a particular room or area is occupied. Conventional techniques will often begin regulating the HVAC operation for energy savings when the system determines that a room or area is unoccupied. Accordingly, it is important to be able to accurately detect occupancy.